PARIS - Salty water just below the surface of Mars could hold enough oxygen to support the kind of microbial life that emerged and flourished on Earth billions of years ago, researchers reported Monday (Oct 22).
In some locations, the amount of oxygen available could even keep alive a primitive, multicellular animal such as a sponge, they reported in the journal Nature Geosciences.
"We discovered that brines" - water with high concentrations of salt - "on Mars can contain enough oxygen for microbes to breathe," said lead author Vlada Stamenkovic, a theoretical physicist at the Jet Propulsion Laboratory in California.
"This fully revolutionises our understanding of the potential for life on Mars, today and in the past," he told AFP.
Up to now, it had been assumed that the trace amounts of oxygen on Mars were insufficient to sustain even microbial life.
"We never thought that oxygen could play a role for life on Mars due to its rarity in the atmosphere, about 0.14 per cent," Stamenkovic said.
By comparison, the life-giving gas makes up 21 per cent of the air we breathe.
On Earth, aerobic - that is, oxygen breathing - life forms evolved together with photosynthesis, which converts CO2 into O2. The gas played a critical role in the emergence of complex life, notable after the so-called Great Oxygenation Event some 2.35 billion years ago.
But our planet also harbours microbes - at the bottom of the ocean, in boiling hot springs - that subsist in environments deprived of oxygen.
"That's why - whenever we thought of life on Mars - we studied the potential for anaerobic life," Stamenkovic.
LIFE ON MARS?
The new study began with the discovery by Nasa's Curiosity Mars rover of manganese oxides, which are chemical compounds that can only be produced with a lot of oxygen.
Curiosity, along with Mars orbiters, also established the presence of brine deposits, with notable variations in the elements they contained.
A high salt content allows for water to remain liquid - a necessary condition for oxygen to be dissolved - at much lower temperatures, making brines a happy place for microbes.
Depending on the region, season and time of day, temperatures on the Red Planet can vary between minus 195 and 20 deg C.
The researchers devised a first model to describe how oxygen dissolves in salty water at temperatures below freezing.
A second model estimated climate changes on Mars over the last 20 million years, and over the next 10 million years.
Taken together, the calculations showed which regions on the Red Planet are most likely to produce brine-based oxygen, data that could help determine the placement of future probes.
"Oxygen concentrations (on Mars) are orders of magnitude" - several hundred times - "greater than needed by aerobic, or oxygen-breathing - microbes," the study concluded.BRASILERAS Canvas Slip-on Shoes in White ~ size 8.5 ~ NEW ~ $30GRASSHOPPERS BLACK SHOES WOMENS SIZE 6 1/2 M , RK Collection Buckle Slides REID - 08 Sandals in Yellow ~ size 39-40 ~ NWBEarth Mary Jane Kalso Comfort Shoes Slip On Brown Casual Ballet Flats Womens 7BWomen's Jessica Simpson Mandayss Shoes Beige Round Toe Textile Flats Size 6 M919 Tory Burch Travel Minnie Black Leather Black Logo Ballet Flat Size 9.5 M , LACOSTE Derby Cuir Vert T 4.5 UK soit 37.5 FR TBE , CC Resorts Sugar Size 9.5 Casual Shoes Sneakers Elasticized Woven Soft Comfort , ECCO Sense Light LADIES Size US 9-9.5 Black Slip On Shoes X13-2061 , Adrianna Papell Women's Stevie Ballet Flat, Dark Powder, Size 8.0CONVERSE One Star black sequin slip on sneakers women's size 8 , NIKE DART 7 Gray Silver Red Women's Running Trail Athletic Shoes US 8 Euro 39TredSafe Medical Walking Shoe Size 6.5W Sally Style LeatherSoft Style Women's Faeth Flat - Choose SZ/ColorHCD Hot Chocolate Design Chocolaticas Strawberry US 8 Shoes 38 Mary Jane Flat , KEDS BALLET FLATS 27-33 NEW craze kedette dolce cherry eleanor kid's shoes , Women Sport Shoes Light Weight Sneakers Walking Breathable Trainer Athletic Flat , Womens Breathable Fashion Sneakers Platform Wedge High Heel Ankle Boots Creepers , Nike Lunarglide 3 Womens US Size 6 EUCSkecher’s Go-Run 400 Gym Shoes (7) , DC Women's Heathrow SE Shoe - Navy / White - NewReef Women's "Walled Low LE" Shoe size 5 WhiteUnder Armour UA Charged Lightning Women's Running Shoes Sneakers Grey 9.5M New , Skechers Hi-Lites - Liquid Bling Rosegold Womens Fashion Sneaker Size 9.5M , NEW Women Asics FUSEX LYTE T670N.9901 Oynx/White/Turquoise Running Shoe Sz 7 , Puma Soleil V2 Comfort Fun Black Women Walking Shoes 9 , Skechers Womens Shape-Ups 7.5 Toning Walking Shoes Gray/Pink/SilverConverse All Star Womens Sneakers Size 10 White & Gold Polka Dot Canvas Shoes , Women Reebok BD4815 Train Fusion LMT Training shoes grey black white sneakers , Skechers Active Biker Step Up Mary Janes Black Leather Sz 8
"Our results do not imply that there is life on Mars," Stamenkovic cautioned. "But they show that the Martian habitability is affected by the potential of dissolved oxygen."